The present invention relates generally to improvements in embolic protection systems and methods. In particular, the present invention relates to an improved embolic protection device and system for enabling movement thereof through a patient""s tortuous vasculature to a location distal to an interventional procedure site for deployment.
A variety of non-surgical interventional procedures have been developed over the years for opening blood vessels in a patient which are stenosed or occluded by the build up of plaque or other substances on the walls of the blood vessel. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter.
One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient""s arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel.
Other procedures destroy or remove the plaque build up from the walls of the blood vessel. Laser angioplasty utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy utilizes a cutting blade which is rotated to shave the deposited plaque from the arterial wall. A vacuum catheter may be used to capture the shaved plaque or thrombus from the blood stream during this procedure.
In another widely practiced procedure, the stenosis can be treated by placing a device known as a stent into the stenosed region to hold open and sometimes expand the segment of the blood vessel or other arterial lumen. Stents are particularly useful in the treatment or repair of blood vessels after a stenosis has been compressed by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are usually delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel and help maintain it in an open position.
The above non-surgical interventional procedures, when successful, avoid the necessity of major surgical operations. However, there is one common problem associated with all of these non-surgical procedures, namely, the potential release of embolic debris into the bloodstream which can occlude distal vasculature and cause significant health problems to the patient. For example, during deployment of a stent, it is possible that the metal struts of the stent can cut into the stenosis and shear off pieces of plaque which become embolic debris that can travel downstream and lodge elsewhere in the patient""s vascular system. Pieces of plaque material can sometimes dislodge from the stenosis during a balloon angioplasty procedure and become released into the bloodstream. Additionally, while complete vaporization of plaque is the intended goal during a laser angioplasty procedure, particles are not always fully vaporized and may enter the bloodstream.
When any of the above-described procedures are performed, for example, in the carotid arteries, the release of emboli into the circulatory system can be extremely dangerous to the patient. Debris that is carried by the bloodstream to distal vessels of the brain may cause these cerebral vessels to occlude, resulting in a stroke, and in some cases, death. Therefore, although carotid percutaneous transluminal angioplasty has been performed in the past, the number of procedures performed has been limited due to the justifiable fear of causing an embolic stroke should embolic debris enter the bloodstream and block vital downstream blood passages.
Medical devices have been developed to address the problem of debris or fragments entering the circulatory system following treatment by one of the above-identified procedures. One approach has been to cut any debris into minute sizes which pose little chance of becoming occluded in major vessels within the patient""s vasculature. However, it is often difficult to control the size of the fragments which are formed, and the potential risk of vessel occlusion still exists, making such procedures in the carotid arteries a high-risk proposition.
Other techniques which have been developed to address the problem of removing embolic debris include the use of catheters with a vacuum source which provides temporary suction to remove embolic debris from the bloodstream. However, such systems still present drawbacks since the vacuum catheter may not always remove all of the embolic material from the bloodstream and the powerful suction could cause additional damage to the patient""s vasculature.
Techniques which have had some limited success include the placement of an embolic protection device such as a filter or trap downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. Such embolic protection devices are adapted to enable the capture of embolic debris which may be released into the bloodstream during the treatment, while still allowing a sufficient amount of oxygenated blood to flow past the device to supply vital organs downstream from the treatment site.
However, there have been problems associated with embolic protection devices, particularly during the expansion, deployment, and formation of the embolic protection device within the blood vessel. The deployment of an embolic protection device may not result in full expansion of the device to properly seal off the circumference of the inner wall of the blood vessel, particularly when the embolic protection device is deployed in tortuous locations having sharp bends. The length of the embolic protection device itself may result in partial collapse of its structure due to lateral loading from the sharp bend in the vessel walls, thereby causing a loss of apposition between the embolic protection device and wall. This can result in embolic material bypassing the filter.
There is a need for an improved system for treating stenosis in body vessels having sharp bends while enabling an embolic protection device to move through a patient""s tortuous vasculature to a location distal to an interventional procedure site. Such a system should expand so as to efficiently and effectively seal off the entire circumference of the inner wall of the body vessel, capture embolic material, and prevent embolic material from bypassing the embolic protection device. The system should be relatively easy for a physician to use, while enabling the effective delivery and recovery of a filtering system capable of removing embolic debris released into the bloodstream. The invention disclosed herein satisfies these and other needs.
The present invention, in general, provides a filtering device for capturing and removing embolic debris from a body vessel and a system for insertion and removal of the filtering device. Embolic debris may be created during the performance of a therapeutic interventional procedure, such as a balloon angioplasty or stenting procedure. The present invention is potentially useful when performing balloon angioplasty, stenting procedures, laser angioplasty or atherectomy in critical body vessels, such as the carotid, renal, and saphenous vein graft arteries, where the release of embolic debris into the bloodstream could possibly occlude the flow of oxygenated blood to the brain or other vital organs which can cause devastating consequences to the patient.
In one aspect, the present invention includes a filtering device. The filtering device is adapted to expand against a body vessel wall to seal off the inner surface thereof, thereby preventing embolic material from bypassing the filtering device and lodging in and blocking body vessels downstream from an interventional procedure site. The filtering device is further adapted for maneuverability through tortuous anatomy having tight bends and for implantation in a curved portion of a body vessel. The present invention is potentially useful for enabling an interventional procedure to be performed in vital arteries, such as the carotid arteries, in which critical downstream body vessels can become blocked with embolic debris, including the main body vessels leading to the brain or other vital organs and in which effective implantation of an embolic protection device is often complicated by sharp bends in the body vessel. As a result, the present invention provides the physician with a higher degree of confidence in the efficient operation of the filtering device for the collection and removal of embolic debris from the body vessel when performing high-risk interventional procedures.
More particularly, the filtering device may have a pre-formed expandable shape and may include a guide wire, a pre-formed expandable basket or cage, filter material, and one or more hinges. The guide wire includes a distal end adapted to be positioned within the body vessel and to extend to a position distal to an interventional procedure site. The pre-formed expandable cage is adapted to engage the distal end of the guide wire and enables the filtering device to expand against and seal off the inner surface of a body vessel wall upon deployment. Filter material attached to the expandable cage facilitates blood flow therethrough while capturing for removal embolic debris released during an interventional procedure. The hinge provides added flexibility to allow the filtering device to be maneuvered through tortuous anatomy and to be deployed in a body vessel having sharp bends without deforming the cage.
Undeformed expansion of the expandable cage precludes the formation of a gap between the filtering device and the body vessel wall, through which embolic material may otherwise flow. The hinge facilitates maneuvering the filtering device through tortuous anatomy by allowing the cage to move independent of the guide wire while still maintaining its connection to the guide wire. Furthermore, the hinge reduces the tendency of the cage to partially collapse when deployed in a body vessel having a sharp bend due to lateral loading from the vessel walls. Moreover, the hinge ensures that the cage will maintain proper wall apposition, thereby providing effective blood filtering and embolic debris capture.
In another aspect, the present invention includes a system for delivering the filtering device through tortuous anatomy, deploying the filtering device in a body vessel at a location distal to an interventional procedure treatment site, and removing the filtering device with the captured embolic material. The system includes a delivery sheath and the aforementioned filtering device adapted to be retained in an unexpanded state by the delivery sheath. An obturator may be provided at the distal end of the guide wire to facilitate maneuvering the system in the patient""s vasculature. In one configuration of the present invention, the hinge is located relative to the expandable cage to allow the cage to move independently from the axial direction defined by the portion of the guide wire which is distal to the expandable cage while still maintaining a connection between the cage and guide wire. In this manner, the hinge acts somewhat like a universal joint allowing the free articulation of the expandable cage on the guide wire to provide additional flexibility to the composite cage/guide wire, especially in tight bends in the patient""s vasculature. The hinge also allows the effective length of the cage to be reduced, which helps resist the tendency of the cage to partially deform when positioned at sharp bends, thus precluding the formation of a gap between the cage and the body vessel wall. In another configuration of the present invention, a hinge is located so as to allow the cage to move independently from the axial direction defined by the portion of the guide wire which is proximal to the expandable cage while still maintaining a connection between the cage and guide wire. In still another configuration of the present invention, hinges are located so as to allow the cage to move independently from the axial directions defined by both the portion of the guide wire that is proximal to the expandable cage and the portion of the guide wire that is distal to the expandable cage while still maintaining a connection between the cage and guide wire, thereby further reducing the lateral loading on the cage due to sharp bends in the body vessel.
The above objects and advantages of the present invention, as well as others, are described in greater detail in the following description, when taken in conjunction with the accompanying drawings of illustrative embodiments.